The sacroiliac joints, on either side of the spine, are located at the very bottom of the back. These joints sit between the sacrum, or vertebrae S1-S5 and the Ilia, or hip bones.
The sacroiliac joint is in the low back where the spine meets the pelvis. Sacroiliac joint pain is discomfort in this area. This pain is a symptom that may come from a number of conditions or diseases.